Hatred has destructive properties. It has pushed even the greatest scholars to commit the ugliest crimes. If you study the history of the caliphate, there were many periods that the caliphs were changed every year. Even today there are countless bombs that explode in Iraq, Afghanistan etj.... Even from my experience I feel that it destroys the properties of the heart and pushes me towards sins and kufr. My question is:. Is it allowed not to hate anyone including ibliss, dajjal and all other evil creatures with the thought that it is none of my business whether they are good or bad and with the thought that my heart feels and becomes much better when it doesn't hate anyone?
"Is it allowed" - No.
Firstly, being apathetic towards people who do bad things is a sign of someone who doesn't have a heart (i.e., either the heart is cold or numb). Hating people who do bad things is a natural human response and shows that you care for what is right.
Secondly, any emotion can lead people to commit great crimes. Even "love" can lead people into sins like fornication or adultery. Every emotion has to be properly managed, controlled and expressed in a halal, fair way. It is no different for hatred.
Thirdly, hating is established as being part of Islam. (Read this post about Al Wala Wal Bara - loving and hating for God's sake - even Prophet Abraham [pbuh] said he hates disbelievers). Hate is what keeps us away from those evil creatures and prevents us from becoming one of them.
Bottom line: Suppressing the natural human feeling of hatred is bad for the heart, not good for it.